See who left an emoji reaction

[gnprice]

I.e., this Zulip feature: https://zulip.com/help/emoji-reactions#viewing-who-reacted-to-a-message

This is less critical than it would have been years ago, because we already show the names of who reacted when there are up to 3 of them. But once there are more, we just show counts, and the user may want to see specifically who left the reactions.

Design

The design for this is in Figma: https://www.figma.com/design/1JTNtYo9memgW7vV6d0ygq/Zulip-Mobile?node-id=5878-1516&t=mBhvNBmPS0sBxGKG-0

Screenshot:

Design discussion: https://chat.zulip.org/#narrow/channel/530-mobile-design/topic/View.20Reactions.20ModalBottomSheet/near/2013460

The green dot (presence indicator) on the avatars is out of scope for this issue.